tools/setlocalversion: Update from the Linux Kernel

Several bugfixes have occurred upstream since this script was imported
into U-Boot.  In particular, the script currently in U-Boot does not
describe commit f8bbb4da correctly,
resulting in a version of "2011.09" instead of "2011.09-01460-gf8bbb4d".

With that commit checked out, the command "git name-rev --tags HEAD"
gives this result:
  HEAD tags/v2011.12-rc1~30^2

Then the "changes" regex does not match because of the trailing '^2':
  grep -E '^HEAD[[:space:]]+(.*~[0-9]*|undefined)$'

The new version of tools/setlocalversion in the kernel correctly handles
those situations by using different plumbing commands.

The version from the kernel is not directly usable as it does not append
the full GIT version that U-Boot expects unless the right config options
are set (CONFIG_LOCALVERSION_AUTO=y).  Other than a few minor changes
for Kconfig, the imported version is very similar to Linux v3.2-rc4.

Signed-off-by: Kyle Moffett <Kyle.D.Moffett@boeing.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Mike Frysinger <vapier@gentoo.org>
Acked-by: Mike Frysinger <vapier@gentoo.org>